Hungry humpbacks?
Are the
great whales facing a food shortage in the Bay of Fundy?
Should herring fishing be scaled back to protect the food supply for whales?
by Debbie
MacKenzie, August 2004
Naturalists in western Nova Scotia, Atlantic Canada, are increasingly concerned that a declining food supply is causing stress to humpbacks and other whales that spend summers feeding in the Bay of Fundy.
The richest food for whales in the area, herring, is also caught by fishermen, and it is now thought that the intensity of the competition is working to the disadvantage of the whales. The worry that humpback whales are having difficulty finding enough food is based on observations by people most familiar with their habits: whales are now spending more days on the feeding grounds, and they seem to be eating relatively more lower-quality food (shrimp-like krill versus high-fat herring). Whale watching tour operators in the Digby Neck area have organized a petition asking the Department of Fisheries and Ocean (DFO) to prohibit herring fishing by purse seiners near the Long Island shore when whales are in the area. However, there is no indication that DFO has taken their request seriously. Adding to the concern, DFO has reported a recent unanticipated “deterioration” of the Bay of Fundy herring stock (DFO, 2004). However, DFO seems to view this only as a problem that might adversely affect herring fishermen, rather than something that might threaten the survival of whales. A significant commercial herring fishery is routinely conducted in feeding areas used by the whales, but are there convincing signs of trouble? How are the whales faring? And what about the herring?
1. Why
worry about the food supply for whales in the Bay of Fundy, an unusually fertile
ocean area?
2. The importance of maintaining herring stocks: how do fisheries
managers ensure that enough herring is left in the sea to feed the whales?
3. What is wrong with herring, and with herring conservation, in
the Bay of Fundy?
4. Will ocean managers try to take corrective action? What might
this be?
5. What is more profoundly wrong in the Bay of Fundy?
6. What is the value of whales?
7. References
1. Why worry about the food supply for whales in the Bay of Fundy, an unusually fertile ocean area?
Humpback whales are massive animals, growing to about 50 feet in length and 50 tons in weight. Capable of living over 90 years, these mammoth whales have huge appetites, and they need more than a ton of food daily. The humpback is one of the species of “great whales” that were driven nearly to extinction by the whaling industry, and current numbers remain far below the original population size. In the years since whaling stopped, humpback whales have made gains, but whale population numbers have recovered far more slowly than scientists anticipated they might. The availability of food for whales has not generally been on our “saving the whales” worry list, but perhaps it should be.
What would whales do to compensate for a decline in their food supply?
Systematic observations and records kept since the 1980s show that humpback whales are now arriving earlier in the year to feed in the Bay of Fundy, and that they are staying later on their feeding grounds, than was their habit a few decades ago. The annual winter migration south involves several months of fasting for these whales, who must survive on blubber accumulated while feeding in northern waters. Is this becoming a greater challenge? Why have the whales lengthened their feeding period and shortened their fast? Recently, some humpback whales have been observed to be overwintering in the Bay of Fundy, in contrast to the long observed pattern of their mass exodus to the warm Caribbean waters each winter. Pregnant female humpback whales must migrate to the warmer waters to deliver and nurse their young, and this is also where mating occurs.
Humpback whales belong to the “rorqual” family of whales. Pleated throats enable them to take in huge gulps of seawater and then filter out small fish and krill by pushing the water out through baleen plates. Whale watchers in the Bay of Fundy have recently noticed relatively less herring-feeding, and more krill-feeding, being done by humpback whales. This subtle trend may signal a detrimental shift in whale nutrition. A dietary shift away from small oily fish like herring, and towards krill, has been noted recently in some seabird populations in Atlantic Canada, and this change has been associated with increased levels of starvation, especially of the young.
Anecdotes involving individual whales are not normally given much attention by scientists. However, last winter the death of a juvenile male humpback whale in the Bay of Fundy, seemingly from starvation, added to the level of concern of the whale watchers. People understand very little about these things, but we do know that for wild mammals and birds in general, the failure to gain proficiency in self-feeding, after the parental food supply ends, is a common point at which starvation controls animal populations. Newly weaned, inexperienced young whales might be particularly vulnerable to starvation, should there be a decline in the availability of herring in the Bay of Fundy.
Herring enliven the sea. A school of herring swimming near the surface can be seen as a darkened swath of agitated water, something like a wind squall. But naturalists working in the whale watching industry off Digby Neck for many years now report seeing remarkably fewer visible signs of herring in the area, both of herring near the surface and of sonar echoes from deeper water, as fewer herring blips are appearing on the electronic “fishfinders.”
More months spent feeding and gaining weight, a possible dietary shift toward crustaceans, and the failure of all humpback whales to migrate south for the winter…might these be important early warning signs?
There is most likely a threshold level of herring availability, that, if it is crossed, will tip the humpback whales into serious trouble. Where this level is, we do not know, but the whales’ need for food, as a part of “ocean ecosystem integrity” and “maintaining biodiversity,” is supposed to take precedence in Canada over the needs of the fishing industry (this is included in federal law, under Canada’s Oceans Act.) Signs of food stress in the still-diminished humpback whale population should therefore be taken seriously by DFO.
Direct assessment of the health of wild whales is very difficult, even for a species as “friendly” as the humpback. Subtle signals must be observed if we hope to assess trends in the nutritional status of a protected whale population. With no current hunting of humpback whales, scientists cannot measure their weight, or blubber thickness, or analyze their stomach contents, for instance. We can only watch for behaviour changes, including feeding habits and the distribution of whales, and perhaps seek clues such as the length of the interval between consecutive births, and the rate of survival to maturity of the young whales. Fecal analysis might help to reveal any changing trends in food intake.
Unfortunately, DFO seems to have no program of systematically monitoring these aspects of whale biology, although they do have an official mandate for the “stewardship” of both the whales and their food supply in Canadian waters. DFO’s recent failure to predict trends and to scientifically “manage” the restoration of depleted sectors of whale food in the Bay of Fundy (herring) does not bode well for their ability to ensure long-term security for whales.
The only whale-food protective tool that DFO possesses is its power to restrict fishing. However, curtailing a herring fishery for the benefit of whales is an unprecedented move, and an idea that will lead us into the contentious arena of conflict between fishermen and the natural predators of fish. (A reluctance on the part of scientists to open this particular can of worms in the Bay of Fundy is understandable, considering the ongoing horrors of Canadian efforts to “manage” a similar relationship between seals, cod and fishermen.) A few years ago, DFO briefly included a comment on trends in whale distribution along the Long Island shore in its herring assessment for the Bay of Fundy (DFO, 2000), but this information has been omitted in more recent publications (…possibly because the indicator was becoming negative?)
2. The importance of maintaining herring stocks: how do fisheries managers ensure that enough herring is left in the sea to feed the whales?
In the Bay of Fundy, herring is a crucial “forage fish,” a rich, abundant food that helps to fatten whales, seabirds and larger fish. Fish like herring, called “small pelagics,” commonly fill this ecological role in all temperate zone oceans. Other similar small schooling fish species, rather than herring alone, dominate elsewhere. Capelin fills the major forage fish role in waters to the north, off Newfoundland and Labrador, and capelin has also long been a target of commercial fisheries. Decades ago, scientific recognition of the importance of capelin in the wider ecosystem led to the setting of lower-than-usual commercial catch quotas for these fish.
“Capelin are eaten by many predators including seals, whales, cod, Greenland halibut, salmon and seabirds. They are considered to be a key element in the food chain. Because of this prominent position in the ecosystem a conservative approach to their management has been adopted. In the late 1970s, scientists recommended that no more than 10% of the projected mature biomass be removed annually in a commercial fishery.” (DFO, 2000b)
The “no more than 10%” rule of thumb therefore seems to be a strategy used by DFO to ensure that enough forage fish are left in the water to sustain whales. Herring fisheries along the Atlantic coast of Nova Scotia have been likewise limited to a 10% harvesting limit, after following a “survey, assess, then fish <10%” protocol (DFO, 2004a). However, the herring fishery conducted in the Bay of Fundy has been granted a 20% upper harvest limit, twice the conservative 10% limit used elsewhere (DFO, 2004a). DFO’s relative lack of caution in setting quotas for the herring fishery in the Bay of Fundy may relate to the strong presence of commercial herring fisheries in this area (a political consideration?), or perhaps to the assumption that the Bay of Fundy is naturally more productive and resilient than other ocean areas. It seems reasonable, however, that any sign of deterioration in the Bay of Fundy herring stock should be met with, at the very least, a prompt adoption of the 10% harvesting rule of thumb that has been applied to forage fish, including herring, elsewhere in Atlantic Canada.
3. What is wrong with herring, and with herring conservation, in the Bay of Fundy?
DFO has reported a recent, unexplained and worsening “deterioration” in the status of the herring population in the Bay of Fundy (DFO, 2004a). The crucial problem is that too many herring are dying at young ages, leaving a fish population that is made up disproportionately of small, young fish. Practically no herring are found today that are more than 7 years old, although herring survived up to 20 years in the past. This recent “age contraction” of the herring population is a classic warning signal of “overfishing,” and scientists have not explained why this is occurring in the Bay of Fundy. A major disappointment for the herring managers occurred in 2003, when the group of young herring that were born in 1998, and that were “confirmed” to be a “dominant year class” (DFO, 2003a, Power et al, 2003) by the time they were four years old in 2002, underwent a sudden and mysterious decline at age five (DFO, 2004a). Why? What killed them? This is a very ominous sign.
Another persistent signal of deterioration in the Scotia – Fundy herring stock has been a marked decline of spawning activity in certain traditional egg-laying areas for herring. Without specifying what additional measures should be taken, the herring assessment scientists have commented on the failure of their recent rebuilding strategies only with “There has been insufficient progress towards conservation objectives in recent years.” (DFO, 2004a)
Returning to consideration of the petition to stop herring seiners from fishing along the Long Island shore, it seems that DFO has enabled a second double standard to work against whales feeding at Long Island. Not only can twice the usual amount of forage fish be taken overall in the Bay of Fundy, but even this generous guideline for fishermen can be exceeded at Long Island. The bulk of herring caught in the Scotia - Fundy region are taken at a few major herring spawning grounds and on the “mixed feeding aggregation” of herring that is found near Long Island. However, the 20% localized herring harvest limit applies only to herring found on spawning grounds. The requirement to “survey, assess, and then fish <20%” therefore does not apply when the seiners are working at Long Island – because it is not a spawning area. The local impact of the herring fishery on the Long Island feeding aggregation is therefore unregulated and uncertain. More than 20% of the Long Island herring schools might easily be removed by the fishermen, since no rule prevents this. This loophole, plus the traditional concentration of whale feeding at Long Island, and the declining signs of herring in the area, make the Long Island ground a logical first place for DFO to tighten restrictions on herring fishing.
The mounting, negative “overfished” signals in the Scotia - Fundy herring stock seem certain to trigger greater measures for their conservation. But what?
4. Will ocean managers try to take corrective action? What might this be?
With a dwindling herring stock, and possible signs of food-stress in humpback whales, it becomes obvious that herring fishing in the Bay of Fundy should be substantially reduced. Granting the request of the whale watchers for a ban on herring seining near Long Island when whales are feeding there, seems to be only a logical first step that might reasonably be taken by DFO. But how likely is this to occur?
DFO has not yet recommended any changes to the current herring management protocol. But when push comes to shove between the needs of natural fish predators, like whales, and the wishes of the fishing industry, what will happen?
What will Canada do when conflict between fishermen and natural fish predators becomes focused on the charismatic great whales? On the environmental icons, the awesome, entertaining (…even income-generating) humpback whales?
This is part of a larger story, because the sequence of recent changes affecting the Scotia-Fundy herring stock closely parallels what happened to cod in Atlantic Canada a decade ago, prior to the disastrous cod collapse. We are slow learners. In the early 1990’s there was a sudden loss of older codfish, an unanticipated change that occurred too quickly to be accounted for directly by the recent intensity of cod fishing (…and explanatory factors beyond fishing were therefore sought, eventually reaching the (questionable) conclusion that a spell of unusually cold water combined with increased predation by seals had also contributed to the demise of cod.) Cod became very scarce in some parts of their former range, while continuing to be found in other parts, and they were generally smaller. This pattern has also been demonstrated by Scotia – Fundy herring. A great ongoing mystery regarding cod has been the inability of the cod stock to support even a moderate or low level of fishing that was easily tolerated decades earlier. There seems to have been a loss of resilience in the very species, and the cod decline has continued relentlessly. The Bay of Fundy herring stock has similarly supported greater landings in the past than the amounts of herring caught in recent years, without experiencing a wholesale loss of older fish such as has occurred lately. Something fundamental has recently changed for herring, as surely as it did for the cod – and it appears certain to be the same syndrome. However, water temperature is unlikely to be offered as an explanation for the loss of herring in the Bay of Fundy. What about natural predators?
What I think of as the “natural predator culling school of fish stock rebuilding” still holds considerable sway in Canada, as this strategy currently dominates DFO's official "cod recovery efforts" (in the form of the seal cull). The players do not yet realize the futility of their plan, but they carry it out with public approval. The Canadian public, however, is sure to balk at any suggestion that whales be culled in a human effort to rebuild herring stocks. But, if DFO applies the same thinking to the herring situation as it has with the cod…
Will Canadian fishery managers soon make a begrudging tally of the tonnage of herring eaten by whales, similar to their detailed calculations of the tonnage of cod eaten by seals? How might this work out?
The western North Atlantic Ocean population of humpback whales is thought to number about 5000, but the whales tend to concentrate in relatively few feeding areas. The larger fin whale, another gargantuan consumer of herring and krill, is also commonly seen in the Bay of Fundy, and the smaller minke whales are even more numerous. If there are the equivalent of 500 whales eating a ton a day of herring in the Scotia – Fundy region, then whales will soon (in 160 days) consume a quantity of herring that rivals that taken by commercial fisheries (about 80,000 tons per year). Will whales soon be blamed for “overfishing” the herring and for causing the stock deterioration? This is precisely what DFO and the fishing industry have done with seals in the case of the cod collapse. Canadians have been taught and have generally accepted anti-seal and pro-whale sentiments communicated by the media. But this is a twisted view of animals that essentially catch the same small fish, the difference being that seals take one small pelagic fish at a time while whales engulf them by the thousands. Seals, however, are denigrated in the Canadian media as “huge, voracious fish gobblers”…
All of these issues dovetail together: troubles with cod, herring, seals, and whales, in the Bay of Fundy, the Scotian Shelf, the Grand Banks of Newfoundland, and the global ocean…and the deeper relevant truth is that all natural fish predators never cause harm, but instead they act subtly in a manner that is positive and beneficial to the survival of their prey. But unfortunately, marine science has been so focused on supporting the fishing industry that this underlying principle of marine ecology has been missed.
Centuries of fishing has worked to remove the vast majority of the small-fish predators from the sea (most of these were large fish (Choi et al, 2004)), and a central assumption underlying the entire science of “sustainable fisheries” has been that removing these natural marine predators would never cause a decline in the potential re-growth of their prey. However, overwhelming evidence now suggests that this was wrong, and ocean science itself is in severe crisis today along with the fisheries and the fish. It is now very late in the game, people have caused major changes in ocean life, and snowballing signals of instability, stress and falling marine productivity are appearing everywhere, including in the legendary, rich Bay of Fundy. If humans hope to preserve existing marine life and to halt the systematic degradation, then a general “pro-marine life” stance, a respect for the positive power of all natural elements of the now-stressed ocean ecosystem, is the only approach that will work. However, this will require a revolutionary change in human thinking.
5. What is more profoundly wrong in the Bay of Fundy?
The issue of hungry humpback whales and deteriorating herring stocks is only the tip of the iceberg. Disturbing signals of insidious negative change, of declining productivity are broadly evident in the Bay of Fundy. Changes at the shoreline and affecting the bay at large include:
- A gradual long-term
decline in shoreline animal life, including snails,
barnacles and others. This “shifting baseline” has been difficult to
appreciate without a fairly long perspective, but older people familiar with the
coastline can readily see it.
- Concern about the food supply for migrating birds that feed on invertebrates
living in the Bay of Fundy mud flats.
- Declining numbers of clams.
- Declining numbers of worms…which have even triggered battles in recent years over the right of people to dig worms in the last locations where they can be found.
- Depressed groundfish stocks, of cod and other species, that are “rebuilding” more slowly than anticipated.
- Declining condition of lobsters in the Southwest Nova Scotia region (low meat, low protein levels, soft shells, dead and dying lobsters in the catch).
- The imminent extinction of the inner Bay of Fundy Atlantic Salmon.
- Signs of food stress in the endangered right whales that feed in the Bay of Fundy (lengthened calving interval, whales arriving earlier and staying later on feeding grounds).
- Changes in algae, both in seaweeds and in free floating plant-plankton. Shifts in the growth patterns of marine algae are widespread and poorly understood. One negative ramification of the plankton changes has been an increase in the production of biotoxins in the Bay of Fundy (the cause of shellfish poisoning, and also capable of killing whales).
- A pulse of increased bottom productivity (seen in faster growth of scallops) has coincided with a general decline in the community of finfish in the Bay of Fundy. This pattern has been noted previously in other parts of the world, and it seems to reflect a disproportionate amount of plankton production falling to the bottom rather than an increase in overall ocean productivity. This change can therefore also be consistent with declining productivity.
How did DFO fail to anticipate that Bay of Fundy herring were going to decline? They did not “connect the dots” because it seems that fish stock assessment scientists were not trained to work that way. The fishery managers’ focus on a single species and its “biomass” can give a false reassurance of stability when the individual fish making up that biomass may have made subtle compensatory shifts in how they maintain themselves. If their preferred food declines, they will eat something else. All animals will do this; each species will scrape the bottom of the barrel to maintain itself if this becomes necessary.
For example, a given “biomass” of whales might exist in a sea full of herring and easily maintain itself by 5 or 6 months of relatively leisurely feeding. The same biomass of whales might live in a herring-poor environment and need to spend 8 or 9 months feeding on krill. A slight down-shift in ocean productivity would have virtually no effect on the first group of whales but it might eliminate the second. This pattern occurs in fish too, of a loss of a species’ security, or leeway, failing to be reflected in its “biomass” alone. While I have not yet discovered any diet studies on Bay of Fundy herring, a significant diet shift over decades has been recorded elsewhere in Atlantic Canada in small pelagic fish (mackerel, and capelin in the Gulf of St. Lawrence: DFO, 2004b, DFO, 2004c). Subtle negative biological signals seem certain to have been missed by the Bay of Fundy herring stock assessors, and this is why the recent herring stock decline came as a surprise. Current scientific assessment methods for marine species seemingly can allow cod, herring, or whales, to be pushed to the wall without people realizing what is happening.
Incredibly, in retrospect, the Canadian cod collapse did not rock the boat of fisheries science hard enough to change the thinking of our ocean “managers.” Confidence in the standard scientific approach was not seriously shaken. But will the impending herring crash have any greater effect? It certainly should. Will scientists and the public need to see a mass mortality of whales to become alarmed? (…or could people possibly blandly accept this eventuality too, should it occur, telling ourselves that this is just how “nature” works?)
6. What is the value of whales?
“Saving” or protecting whales has a high public sentimental value that has not yet been tested in Canada against the value of herring and other fisheries (…although a poor precedent has been set with seals). We have not yet seen anything suggesting to the public that they ought not to support herring fisheries if they want to see healthy whales continue, but the general public has no concept of the scope of the crisis affecting marine life, and no idea that whales might be facing a food shortage. The “whale cull school of fish stock rebuilding” is not a far-fetched suggestion, because whale culls are now being demanded in other countries for exactly this reason (in Japan, Iceland and Norway). Will whales be killed in Canada to support the continuation of fisheries? Probably. If they are not killed directly, whales risk being killed by starvation for this reason. And the “great whales,” including the humpbacks, stand to be eliminated before their smaller cousins.
From a short-term mercenary viewpoint, the development of tourism based on whale-watching has attached a financial value to living whales that may already rival that of the herring fisheries.
However, the greatest value of whales is intuitively realized by most people, although it is seldom clearly elucidated by scientists: whales contribute directly to the vitality, health and stability of the entire web of life in the sea. And a stable marine ecosystem is crucial not only for the long-term survival of whales, but for our kind too.
Should the Bay of Fundy herring fishery give way to the hungry whales? Yes, absolutely.
Will herring fishermen be hurt financially? Yes.
But far more people stand to be hurt, and more profoundly, if we persist in blindly pulling fish from the sea until the ocean ecosystem degrades to the point where whales can no longer be supported. If Canadians realize that we have been inadvertently undermining the supply of food for whales by fishing, then what will we do?
by Debbie MacKenzie, August 25, 2004
email: CodmotherATbellaliant.net
7. References
Choi, J. S., K. T. Frank, W. C. Leggett, and K. Drinkwater. 2004. Transition to an alternate state in a continental shelf ecosystem. Canadian Journal of Fisheries and Aquatic Sciences 61: 505-510.
DFO, 2000a. 4VWX Herring. DFO Science Stock Status Report B3-03 (2000).
DFO, 2000b. Capelin in Subarea 2 + Div. 3KL. DFO Science Stock Status Report B2-02 (2000).
DFO, 2002. 4VWX Herring. DFO Science Stock Status Report B3-03 (2002).
DFO, 2003a. 4VWX Herring. Can. Science Advis. Sec. Stock Status Rep. 2003/027.
DFO, 2003b. State of the Eastern Scotian Shelf Ecosystem. DFO Ecosystem Status Report 2003/004.
DFO, 2004a. 4VWX Herring. Can. Science Advis. Sec. Stock Status Rep. 2004/034.
DFO, 2004b. Atlantic Mackerel of the Northwest Atlantic in 2003. DFO Can. Sci. Advis. Sec. Stock Status Rep. 2004/018.
DFO, 2004c. Capelin of the Estuary and Gulf of St. Lawrence (4RST) in 2003. Can. Sci. Adv. Secr. – DFO, Stock Status report 2004/001.
Melvin, G. D., L. M. Annis, M. J. Power, K. J. Clark, F. J. Fife, and R. L. Stephenson. 2003. Herring acoustic surveys for 2002 in NAFO Divisions 4WX. Canadian Science Advisory Secretariat Research Document 2003/034.
Melvin, G. D., M. J. Power, L. M. Annis, K. J. Clark, F. J. Fife, and R. L. Stephenson. 2004. Summary of the 2003 Herring acoustic surveys in NAFO Divisions 4VWX. DFO Canadian Science Advisory Secretariat Research Document 2004/034.
Power, M. J., R. L. Stephenson, L. M. Annis, F. J. Fife, K. J. Clark and G. D. Melvin. 2003. 2003 Evaluation of 4VWX Herring. Canadian Science Advisory Secretariat Research Document 2003/035.
Waters, C. L. and K. J. Clark. 2004. 2004 Summary of the Weir Herring Tagging Project, with an Update of the HSC/PRC/DFO Herring Tagging Program. Canadian Science Advisory Secretariat Research Document 2004/032.
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